Effectiveness of the cadmium(II) ion in promoting nitrogen deprotonation. 113 Cd NMR, polarographic, and pH-metric investigations on the Cadmium(II)-N-tosyl-glycinate and Cadmium(II)-N-dansylglycinate systems in aqueous and methanolic systems

13Cd NMR, polarographic, and pH-metric investigations reveal the ability of the Cd2' ion in substituting for the nitrogen-boundhydrogen of the amino acids N-protected by a sulfonic group. In aqueous and methanolic solution, N-tosylglycine and Ndansylglycine interacting with the Cd2+ ion show a pH-dependent binding mode, at increasing pH changing from simple carboxylate to N,O-bidentate ligands. The overall equilibria involving the prevailing complexes are similar to those previously found with the Cu2+ ion, but the stability of the cadmium complexes is lower by factors ranging from IO to lo4. Two binary complexes of formula [CdL,(H,O),] (L = N-tosylglycinate, N-dansylglycinate) were separated in the solid state. X-ray powder spectra and IR data for the complex of N-tosylglycine show that it is isomorphous and isostructural with the analogous complexes with Zn2', Co2+, and Ni2+, in which the ligand is monodentate through the carboxylate group.